using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using JGSY.CMS.LowCode.Platform.Application.DTOs;
using JGSY.CMS.LowCode.Platform.Application.Interfaces;

namespace JGSY.CMS.LowCode.Platform.Application.Services
{
    /// <summary>
    /// 系统设置应用服务实现
    /// 提供系统配置参数的管理功能，包括获取、更新、删除等操作
    /// </summary>
    /// <remarks>
    /// 该服务负责管理系统级别的配置参数：
    /// - 系统基础配置（网站名称、描述等）
    /// - 功能开关配置
    /// - 业务参数配置
    /// - 第三方服务配置
    /// 
    /// 注意：当前实现使用内存存储，生产环境应使用数据库持久化
    /// </remarks>
    public class SystemSettingAppService : ISystemSettingAppService
    {
        private readonly ILogger<SystemSettingAppService> _logger;
        private static readonly List<SystemSettingDto> _settings = new();
        private static long _nextId = 1;

        /// <summary>
        /// 初始化系统设置应用服务
        /// </summary>
        /// <param name="logger">日志记录器</param>
        /// <exception cref="ArgumentNullException">logger为null时抛出</exception>
        public SystemSettingAppService(ILogger<SystemSettingAppService> logger)
        {
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
            InitializeDefaultSettings();
        }

        /// <summary>
        /// 获取所有系统设置
        /// </summary>
        /// <returns>系统设置列表，按类别和键名排序</returns>
        /// <exception cref="Exception">获取设置失败时抛出</exception>
        /// <remarks>
        /// 返回的设置按以下规则排序：
        /// 1. 首先按类别（Category）排序
        /// 2. 同类别内按键名（Key）排序
        /// </remarks>
        public async Task<IEnumerable<SystemSettingDto>> GetAllAsync()
        {
            try
            {
                _logger.LogInformation("获取所有系统设置");
                
                await Task.Delay(10); // 模拟异步操作
                var result = _settings.OrderBy(x => x.Category).ThenBy(x => x.Key);
                
                _logger.LogInformation("成功获取系统设置，数量: {Count}", result.Count());
                return result;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "获取所有系统设置失败");
                throw;
            }
        }

        /// <summary>
        /// 根据ID获取系统设置
        /// </summary>
        /// <param name="id">设置项的唯一标识符</param>
        /// <returns>系统设置信息，不存在时返回null</returns>
        /// <exception cref="Exception">查询设置失败时抛出</exception>
        public async Task<SystemSettingDto?> GetByIdAsync(long id)
        {
            try
            {
                _logger.LogInformation("根据ID获取系统设置: {Id}", id);
                
                await Task.Delay(10); // 模拟异步操作
                var result = _settings.FirstOrDefault(x => x.Id == id);
                
                _logger.LogInformation("根据ID {Id} 查找设置结果: {Found}", id, result != null);
                return result;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "根据ID获取系统设置失败: {Id}", id);
                throw;
            }
        }

        /// <summary>
        /// 添加新的系统设置
        /// </summary>
        /// <param name="dto">系统设置数据传输对象</param>
        /// <returns>添加任务</returns>
        /// <exception cref="ArgumentNullException">dto为null时抛出</exception>
        /// <exception cref="Exception">添加设置失败时抛出</exception>
        /// <remarks>
        /// 添加设置时会自动分配唯一的ID，
        /// 建议在添加前检查Key的唯一性以避免重复配置
        /// </remarks>
        public async Task AddAsync(SystemSettingDto dto)
        {
            if (dto == null) throw new ArgumentNullException(nameof(dto));

            try
            {
                _logger.LogInformation("开始添加系统设置: {Key} = {Value}", dto.Key, dto.Value);
                
                dto.Id = _nextId++;
                _settings.Add(dto);
                
                _logger.LogInformation("系统设置添加成功: {Key} = {Value} (ID: {Id})", dto.Key, dto.Value, dto.Id);
                await Task.Delay(10); // 模拟异步操作
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "添加系统设置失败: {Key}", dto.Key);
                throw;
            }
        }

        /// <summary>
        /// 更新现有的系统设置
        /// </summary>
        /// <param name="id">要更新的设置项ID</param>
        /// <param name="dto">更新后的系统设置数据</param>
        /// <returns>更新任务</returns>
        /// <exception cref="ArgumentNullException">dto为null时抛出</exception>
        /// <exception cref="ArgumentException">指定ID的设置不存在时抛出</exception>
        /// <exception cref="Exception">更新设置失败时抛出</exception>
        public async Task UpdateAsync(long id, SystemSettingDto dto)
        {
            if (dto == null) throw new ArgumentNullException(nameof(dto));

            try
            {
                _logger.LogInformation("开始更新系统设置: ID {Id}", id);
                
                var existing = _settings.FirstOrDefault(x => x.Id == id);
                if (existing == null)
                {
                    throw new ArgumentException($"ID为 {id} 的系统设置不存在");
                }

                existing.Key = dto.Key;
                existing.Value = dto.Value;
                existing.Description = dto.Description;
                existing.Category = dto.Category;
                existing.IsEnabled = dto.IsEnabled;

                _logger.LogInformation("系统设置更新成功: {Id} - {Key}", id, existing.Key);
                await Task.Delay(10); // 模拟异步操作
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "更新系统设置失败: {Id}", id);
                throw;
            }
        }

        /// <summary>
        /// 删除系统设置
        /// </summary>
        /// <param name="id">要删除的设置项ID</param>
        /// <returns>删除任务</returns>
        /// <exception cref="Exception">删除设置失败时抛出</exception>
        /// <remarks>
        /// 如果指定ID的设置不存在，操作不会抛出异常，而是记录警告日志
        /// </remarks>
        public async Task DeleteAsync(long id)
        {
            try
            {
                _logger.LogInformation("开始删除系统设置: {Id}", id);
                
                var existing = _settings.FirstOrDefault(x => x.Id == id);
                if (existing == null)
                {
                    _logger.LogWarning("要删除的系统设置不存在: {Id}", id);
                    return;
                }

                _settings.Remove(existing);
                _logger.LogInformation("系统设置删除成功: {Id}", id);
                await Task.Delay(10); // 模拟异步操作
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "删除系统设置失败: {Id}", id);
                throw;
            }
        }

        /// <summary>
        /// 根据类别获取系统设置
        /// </summary>
        /// <param name="category">设置类别名称</param>
        /// <returns>指定类别的系统设置列表，按键名排序</returns>
        /// <exception cref="Exception">查询设置失败时抛出</exception>
        /// <remarks>
        /// 类别匹配不区分大小写，返回结果按键名升序排序
        /// </remarks>
        public async Task<IEnumerable<SystemSettingDto>> GetByCategoryAsync(string category)
        {
            try
            {
                _logger.LogInformation("根据类别获取系统设置: {Category}", category);
                
                await Task.Delay(10); // 模拟异步操作
                var result = _settings
                    .Where(x => x.Category.Equals(category, StringComparison.OrdinalIgnoreCase))
                    .OrderBy(x => x.Key);
                
                _logger.LogInformation("根据类别 {Category} 获取到 {Count} 个设置", category, result.Count());
                return result;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "根据类别获取系统设置失败: {Category}", category);
                throw;
            }
        }

        private void InitializeDefaultSettings()
        {
            if (_settings.Any()) return;

            _settings.AddRange(new List<SystemSettingDto>
            {
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "SiteName",
                    Value = "JGSY CMS Platform",
                    Description = "网站名称",
                    Category = "General",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "SiteDescription",
                    Value = "Low Code Content Management System",
                    Description = "网站描述",
                    Category = "General",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "MaxFileSize",
                    Value = "10485760",
                    Description = "最大文件上传大小（字节）",
                    Category = "Storage",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "SessionTimeout",
                    Value = "3600",
                    Description = "会话超时时间（秒）",
                    Category = "Security",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "EnableSSL",
                    Value = "true",
                    Description = "启用SSL加密",
                    Category = "Security",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "DatabaseTimeout",
                    Value = "30",
                    Description = "数据库连接超时时间（秒）",
                    Category = "Performance",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "CacheExpiration",
                    Value = "300",
                    Description = "缓存过期时间（秒）",
                    Category = "Performance",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "LogLevel",
                    Value = "Information",
                    Description = "日志记录级别",
                    Category = "Logging",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "EmailEnabled",
                    Value = "true",
                    Description = "启用邮件功能",
                    Category = "Email",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "EmailHost",
                    Value = "smtp.example.com",
                    Description = "邮件服务器地址",
                    Category = "Email",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "DefaultLanguage",
                    Value = "zh-CN",
                    Description = "默认语言",
                    Category = "General",
                    IsEnabled = true
                },
                new SystemSettingDto
                {
                    Id = _nextId++,
                    Key = "DefaultTheme",
                    Value = "light",
                    Description = "默认主题",
                    Category = "General",
                    IsEnabled = true
                }
            });
        }
    }
}
